Conditioned air distribution



March 20, 1962 A. P. JENTOFT Filed May 6, 1960 -PNEUMATIC FLOWCONTROLLER 3| 4; Sheets-Sheet 1 I I 5 2| I Z "I l 5, {/20 l 2 I 11 I L8.I 1 l q I PNEUMATIC I blg E 25 I THERMOSTAT I I 23 I I l I3 I L I PRIORf ART THERMOSTAT PRESSURE HIGH STATIC AIR PRESSURE IN FLOW HOT AIR INLETHOT All-7 D o 0 [NORMAL RA N65! THERMOSTAT PRESSURE INVENTOR.

ARTHUR P. JENTOFT BY 6 I March 20, 1962 A. P. JENTOFT CONDITIONED AIRDISTRIBUTION 4 Sheets-Sheet 2 Filed May 6, 1960 PNEUMATIC FLOWCONTROLLER n y MO M UR u m PT NORMAL RANGEI THERMOSTAT PRESSUREINVENTOR.

ARTHUR P. JEN TOF'I A TORNEY March 20, 1962 A. P. JENTOFT 3,026,041

CONDITIONED AIR DISTRIBUTION Filed May 6, 1960 4 Sheets-Sheet 3 3|PNEUMATIC FLOW CONTROLLER PNEUMATIC THERMOSTAT LOW LOW STATIC STATIC AIRPRESSURE IN AIR PRESSURE IN FLOW HOT AIR FLOW HOT AIR NLET \wm/n INLET\HOTA/R 0 Q O [NORMAL RANGE! O I/VOl-PMAL RANGEI THERMOSTAT PRESSURETHERMOSTAT PRESSURE INVENTOR.

ARTHUR P. JENTOFT BY 4 fl.

ATTORNEY Filed May 6, 1960 A. P. JENTOFT CONDITIONED AIR DISTRIBUTION 4Sheets-Sheet 4 GQ QT 3| PNEUMATIC FLOW CONTROLLER 34 f F A 4 H PNEUMATIC1:; i9 THERMOSTAT 14 INVENTOR.

ARTHUR P. JENTOFT T R EY United States Patent Office 3,026,041 PatentedMar. 20, 1952 3,026,041 CONDITIONED AIR DISTRIBUTION Arthur P. Jentoft,Wexford, Pa., assignor to H. H. Robertson Company Filed May 6, 1960,Ser. No. 27,411 3 Claims. (Cl. 23613) This invention relates to airconditioning systems and more particularly to a method and apparatus forautomatic regulation of room temperature and inlet volume of air flow ina two stream air conditioning system.

Air conditioning systems employing two separate streams of air, hot andcold, are well known in the art. See, for example, US. Patent 2,729,429.Such air conditioning systems operate by providing separate streams ofair which are distributed throughout a building for blending prior todischarge into the rooms of the building. One of these streams ismaintained at a temperature substantially above the temperature which itis desired to maintain within the rooms. The other stream is maintainedat a temperature which is substantially below the temperature which itis desired to maintain in the rooms. By independently throttling the twostreams, a resultant blended stream of conditioned air can be providedfor discharge into the rooms at a blended temperature which willmaintain the desired conditions within the rooms of the building. Goodventilation practice dictates that the conditioned air should besupplied to the individual rooms at a substantially constant volume offlow.

For a clear understanding of the present invention and of problemspresented by two stream conditioned air systems, reference should be hadto the accompanying drawings in which:

FIGURE 1 is a schematic illustration of a prior art mixer box havingautomatic controls suitable for normal operation of two-stream airconditioning systems;

FIGURE 2 is a graphical representation of the normal operation of themixer box illustrated in FIGURE 1;

FIGURE 3 is a graphical illustration of one defect which is inherent inthe operation of the prior art mixer box shown in FIGURE 1;

FIGURE 4 is a schematic illustration of a mixer box according to oneembodiment of the present invention which offsets the inherent defectillustrated in FIGURE 3;

FIGURE 5 is a cross-section illustration of a shuttle valve which isshown schematically in FIGURE 4;

FIGURE 6 is a graphical illustration showing the results achieved byoperation of the mixer box of FIG- URE 4;

FIGURE 7 is a graphical illustration showing another defect which isinherent in the operation of the prior art mixer box of FIGURE 1;

FIGURE 8 is a schematic illustration of an alternative embodiment of thepresent invention which ofisets the inherent defect illustrated inFIGURE 7;

FIGURE 9 is a cross-section illustration of a shuttle valve which isillustrated schematically in FIGURE 8;

FIGURE 10 is a graphical illustration showing the results achieved bythe operation of the mixer box of FIG- URE 8; and

FIGURE 11 is a schematic illustration of a preferred embodiment of themixer box of this invention including the features ah'eady shown inFIGURES 4 and 8.

Every room, group of rooms or portion of a single room in a building maybe considered as a relatively confined zone for the purposes of airconditioning. A continuous supply of conditioned air is introduced intoeach room (control zone) and a corresponding quantity of air is removedfrom the room (control zone) for dissipation or reconditioning andrecirculation.

As shown in FIGURE 1, an individual room or control zone is indicated bythe numeral 10.

Two streams of conditioned air are provided throughout the building andare represented by the numerals 11 (cold air inlet) and 12 (hot airinlet). The two air inlets communicate with a mixer box 13 which isshown in cross-section. A pair of partitions 14, 15 extend across thecavity of the mixer box 13 and divided the cavity into an inlet blendingchamber 16, a mixing chamber 17 and a distribution chamber 18. Thepartition 14 separates the inlet blending chamber 16 from the mixingchamber 17 and has a plurality of directional mixing vanes 19 whichcreate some turbulence as air passes through the portion 14 to provide auniformly mixed stream of blended air. The partition 15 separates themixing chamber 17 from the distribution chamber 18 and has a perforateplate 20 through which air may experience streamline flow. The perforateplate 26 may be a screen, perforated sheet, netting, mesh and the like.Imperforate plates 21 are provided in a slidable mounting in which theymay be extended or retracted to'regulate the cross-sectional area of theperforate plate 21 to regulate the flow of air therethrough.

A pair of pneumatically controlled valves 22, 23 is provided in the coldair inlet 11 and the hot air inlet 12 respectively to throttle the fioWsof air issuing into the inlet blending chamber 16. Air is dischargedfrom the inlets 11 and 12 into the inlet blending chamber 16 whence itpasses between the vanes 19 for uniformity of mixing within the mixingchamber 17. Uniformly blended air passes through the perforate plate 213into the distribution chamber 18 whence it is discharged into thecontrol zone 10 through conduits 24, 25. Additional conduits 26 may beprovided to discharge additional air to other rooms or to differentlocations of the same room. The entire air discharge from thedistribution chamber 18 enters the control zone albeit several differentrooms may reeive the discharge.

An exit conduit 27 is provided to withdraw air from the control zone 10for dissipation or reconditioning and recirculation.

A pneumatic thermostat 28 is maintained within the control zone 10 forcontinuous observation of the temperature therein. A supply stream ofpressurized air is introduced into the thermostat 28 through a supplyconduit 29. The thermostat 28 regulates the pressure of the supply air,usually by bleeding a portion of the air, according to the deviation ofthe actual temperature within the control Zone 10 from a predeterminedtemperature setting of the thermostat 28. Thus a temperature regulatedpressure of the throttled supply air is introduced into a conduit 36which communicates with and operates the pneumatically controlled valve23 in the hot air inlet 12. Normally the supply air in the conduit 29 ismaintained at a pressure of about 17 to 20 pounds per square inch. Thetemperature regulated pressure in the conduit 30 normally has a range ofabout 5 pounds per square inch, that is, from about 8 pounds per squareinch to about 13 pounds per square inch. Hereinafter any conduit whichconfines the temperature regulated pressure and which extends betweenthe thermostat 28 and any other element in the system will be identifiedas the thermostat conduit.

When the temperature Within the control zone It) is below thepredetermined value, the temperature regulated pressure in thethermostat conduit 30 is reduced; when the temperature in the controlzone 10 is above the predetermined value, the temperature regulatedpressure in the thermostat conduit 30 is increased. The pneumaticallyresponsive valve 23 operates to be opened when confronted withrelatively low pressures and to be closed when confronted withrelatively high pressures. Thus the amount of hot air issuing from hotair inlet 12 into the inlet blending chamber 16 is controlled inresponse to deviations of the actual temperature within the control zone19 from a predetermined value.

A substantially constant volume discharge of blended conditioned airinto the distribution chamber 18 is achieved by means of a pneumaticflow controller such as a differential pressure regulator 31. It will beobserved that the perforate plate 24) in the baflie 15 serves as a flowmeasuring orifice. A pair of static pressure sensing tape 32, 33 isprovided to observe the static pressure on each side of the baffie 15and to transmit these static pressures to the differential pressureregulator 31. So long as a constant volume of air passes through theperforate plate 20, a predetermined constant pressure differential willexist between the pressure taps 32, 33. If the volume of air passingthrough the perforate plate 24) exceeds the predetermined value, thepressure differential existing between the pressure taps 32, 33 willincrease. Similarly if the volume of air passing through the perforateplate 2i) is less than the predetermined value, the pressurediflferential existing between the pressure taps 32, 33 will decrease.Accordingly the differential pressure regulator 31 serves to regulate asupply of pressurized air from a conduit 34, usually by bleeding aportion of the air, in response to deviations in the observeddifierential pressure from a predetermined constant value. Thus a flowregulated pressure of the throttled supply air is introduced into aconduit 35. Hereinafter any conduit which confines the flow regulatedpressure and which extends between the differential pressure regulator31 and any other element in the system will be identified as a pressureregulator conduit. If the observed differential pressure is greater thanthe predetermined value, the flow regulated pressure maintained in thepressure regulated conduit 35 increases. It the observed differentialpressure is less than the predetermined value, the flow regulatedpressure maintained in the pressure regulator conduit 35 is decreased.

The perforate plate 20 serves principally to promote a uniform flow ofair from the mixing chamber 17 to the distribution chamber in order thatthe pressure diiierential existing between the chambers 17 and 18 may beaccurately measured by suitable pressure differential measuringapparatus. The pressure regulator conduit 35 communicates with andoperates the pneumatically controlled valve 22 in the cold air inlet 11.Normally the range of the flow regulated pressure maintained within thepressure regulator conduit 35 will be about 5 pounds per square inch,that is, from about 3 pounds per square inch to about 8 pounds persquare inch. High air pressures in the pressure regulator conduit 35tend to close the pneumatically controlled valve 22. Low air pressuresin the pressure regulator conduit 35 tend to open the pneumaticallycontrolled valve 22.

It is thus apparent that the how of hot air from the hot air inlet 12 isregulated in response to the thermostat 28 in such manner that greaterquantities of hot air will be discharged into the inlet blending chamber16 when the actual temperature in the control Zone is below thepredetermined temperature setting. The amount of cold air dischargedinto the inlet blending chamber 16 from the cold air inlet 11 will besufiicient so that the combination of the hot air and cold air whichpasses through the perforate plate 20 is a predetermined volume.

The normal operation of the system illustrated in FIGURE 1 can bedescribed by the graphical representation shown in FIGURE 2. Thevertical axis represents the flow of air from each of the two inlets 11,12. An arrow A indicates the predetermined constant volume of air whichis desired in the control zone It The horizontal axis indicates thetemperature regulated pressure (thermostat pressure) maintained withinthe temperature regulated conduit 39. It will be observed thatincreasing thermostat pressure results in a decreased volume of hot airentering into the inlet blending charnher 16. The amount of cold airdischarged into the inlet blending chamber 16 is supplementarilydependent upon the amount of hot air and is such that the summation ofthe cold air and the hot air is equal to the predetermined constantvolume which is indicated by the arrow A. The arrow B indicates the flowof hot air which is achieved when the pneumatically controlled valve 23is fully opened with a normal static pressure being maintained in thehot air inlet 12. The arrow C indicates that there is no hot airadmitted into the inlet blending chamber 16 when the pneumaticallycontrolled valve 23 is completely closed, corresponding to a hightemperature regulated pressure appearing within the conduit 3%). Undernormal operatin conditions, the system illustrated in FIGURE 1 willperform entirely within the normal range indicated in FIGURE 2. That is,some quantity of air will be admitted into the inlet blending chamber 16from each of the inlets 11 and 12.

The system illustrated in FIGURE 1 exhibits inherent defects in twocircumstances:

Circumstance ].When the control zone 10 is cold and a high staticpressure exists in the hot air inlet 12.

Circumstance 2.When the control zone iii is cold and a low staticpressure exists in the hot air inlet 12.

According to the present invention, mixer box controls are presentedwhich overcome the inherent defects in the two described circumstances.To offset circumstance 1, a shuttle valve is provided in the thermostatconduit which permits the differential pressure regulator to overridethe thermostat as the control parameter for the pneumatically controlledvalve in the hot air inlet. To compensate for circumstance 2, a shuttlevalve is provided in the pressure regulator conduit which causes closureof the pneumatically controlled valve in the cold air inlet in resposeto pressurized supply air when the thermostat pressure falls below itsnormal operating range.

The principal obiect of this invention is to provide a mixer box andcontrols therefor which will automatically regulate the flow of air froma two-stream air conditioning system to maintain a predeterminedtemperature within a control zone while providing ventilation at asubstantially constant volume rate.

A further object of this invention is to provide a mixer box and controlsystem therefor to regulate the flow or" air from a two-stream airconditioning system regardless of the static pressure fluctuations inthe streams.

These and other objects and advantages of the present invention willbecome apparent from the following detailed description.

Circumstance I.When the control zone 10 is cold and a high staticpressure exists in the hot air inlet 12.

Consider the system shown in FIGURE 1 when the control zone 10 is cold,i.e., at a temperature below tr e predetermined temperature. Decreasedtemperature regulated pressure in the thermostat conduit 30 will causethe pneumatically controlled valve 23 to move to fully open position.If, at this time, the static pressure within the hot air inlet 12 isexcessive, it is possible that the hot air issuing into the inletblending chamber 16 has a greater volume than the predetermined volumewhich is controlled by the differential pressure regulator 31.Accordingly the pressure taps 32, 33 will sense an excessivedifferential pressure; hence an increasing flow regulated pressure willappear in the pressure regulator conduit 35 to cause the pneumaticallycontrolled valve 22 to close completely. The differential pressureregulator 31 at that point has fully compensated the dependent variablewhich it controls yet has not limited the volume of air flowing throughthe perforate plate 20 to the predetermined value. The result is asshown in FIGURE 3 where it appears from the arrow D that the flow ofcold air has been terminated yet the total flow, representingexclusively hot air, exceeds the predetermined value (indicated by thearrow A) as shown by the shaded area 34. Thus when circumstance 1develops, an excessive volume of air is introduced into the control zone18 through the conduits 24, 25.

The embodiment of this invention illustrated in FIG- URE 4 avoids thedifi'iculties just described with reference to circumstance l. Theessential elements of FIG- URE 4 are the same as those illustrated inFIGURE 1 and corresponding numerals refer to corresponding elements.

A shuttle valve 40 is provided having two inlet connections and oneoutlet connection. A thermostat conduit 30a connects the thermostat 28with one of the inlet connections of the shuttle valve 40. A pressureregulator conduit 41 extends from the pressure regulator conduit 35 tothe other inlet connection of the shuttle valve 49. A pneumatic valveoperating conduit 42 connects the outlet of the shuttle valve 40 withthe pneumatically controlled valve 23.

The shuttle valve 40 is more clearly illustrated in FIG- URE 5.Essentially the shuttle valve 49 is formed from two casing halves 43 and44 which are joined together by means of bolts 45. A flexible diaphragm46 separates the casing halves 43 and 44. Cavities in each of the casinghalves 43 and 44 form a right hand chamber 47 and a left hand chamber 48separated by the flexible diaphragm 46. A conduit 49 is provided in thecasing half 43 for communication between the thermostat conduit 39a andthe right hand chamber 47. A conduit 50 is provided in the casing half44 for communicating between the pressure regulator conduit 41 and theleft hand chamber 48. A conduit 51 extends through both of the casinghalves 43, 44 and communicates between the right hand chamber 47 and thepneumatic valve operating conduit 42. A threaded needle adjustment screw52 extends through the casing half 43 to provide an adjustablerestriction in the conduit 51. A conduit 53 is provided in the casinghalf 44 between the left hand chamber 48 and the pneumatic valveoperating conduit 42. A central boss 54, 55 extends inwardly from eachof the casing halves 43, 44 respectively.

It will be apparent that the air pressure of the thermostat conduit 33ais presented in the right hand chamber 47 through the conduit 49 whereasthe air pressure of the pressure re ulator conduit 41 is presented inthe left hand chamber 48 through the conduit 50. Under normal operatingconditions, the pressure in the right hand chamber 47 will exceed thepressure in the left hand chamber 48 and consequently the diaphragm 46will be displaced to the left to cover the chamber openings of theconduits 50, 53 which are presented in the left hand chamber 48 in theboss 55. Accordingly the conduits 49, 51 will be in communication withthe right hand chamber 47 and the air pressure of the thermostat conduit3% will be transmitted through the conduit 49, the right hand chamber47, the conduit 51 to the pneumatic valve operating conduit 42. Ineffect, under normal operating conditions, there is a direct conduitconnection between the thermostat 28 and the pneumatically controlledvalve 23 and hence the system shown in FIGURE 4 normally functionsexactly as the system shown in FIGURE 1.

However when circumstance l is presented, i.e., the temperature withinthe control zone 16 is below the predetermined value and a high staticpressure exists in the hot air inlet 12, the inherent defect illustratedin FIG- URE 3 is ofiset by the apparatus shown in FIGURE 4. The defectis offset in the following manner. Because of the low temperatureexisting in the control zone 10, the air pressure in the thermostatconduit 34a is a low value tending to open the pneumatically controlledvalve 23 to a maximum open position. Similarly the air pressure in thepressure regulator conduit 35 is a maximum tending to close thepneumatically operated valve 22. Once the pneumatically operated valve22 is fully closed, the differential pressure regulator 31 will continueto increase the air pressure in the pressure regulator conduit 35 in aneffort to correct for the excessive differential pressure which is beingsensed through the pressure taps 32, 33. The further increasing pressureis transmitted through the conduit 41 into the shuttle valve 40 throughthe conduit 50. When the pressure in the left hand chamber 43 exceedsthe pressure in the right hand chamber 47, the diaphragm 46 moves fromleft to right covering the boss 54 and opening the boss 55, Thus theincreased pressure from the conduit 41 is transmitted through theconduit 5% into the left hand chamber 48 through the conduit 5;: to thepneumatic valve operating conduit 42 where it exerts a pressure againstthe pneumatically operated valve 23 tending to cause it to move toward aclosed position until only the predetermined volume of air is issuingthrough the perforate plate 20.

Normal operation is restored when the static pressure in the hot airinlet 12 is reduced to a normal value or when the temperature in thecontrol zone 10 rises to a value closer to the predetermined value. Ifthe static pressure in the hot air inlet 12 decreases to a normal value,the air issuing from the conduit 12 into the inlet blending chamber 16will be less than the predetermined value and the air pressure in thepressure regulator conduits 35 and 41 will decrease to allow thediaphragm 46 to move against the boss 55 as in normal operation.Alternatively a closer approach to the predetermined temperature in thecontrol zone 1% will result in an increase in the air pressure in thethermostat conduit 30a which will cause the diaphragm 46 to move againstthe boss 55 and at the same time exert a closing tendency through thepneumatic valve operating conduit 42 against the pneumatically operatedvalve 23.

The correction achieved by the system illustrated in FIGURE 4 is showngraphically in FIGURE 6. When the flow of cold air has been terminatedcompletely (see the arrow D), the shuttle valve 40 automaticallyswitches the control parameter from the thermostat to the differentialpressure regulator so that the desired volume of air, as indicated bythe arrow A, is not exceeded.

A typical situation which might create circumstance 1 would be presentedwhen an individual within the control zone 10 opens a window or a doorin cold weather to allow a substantial quantity of cold air to enter thecontrol zone 10 and create a decrease in the actual temperature therein.If this situation should develop at a time when an excessive staticpressure appears in the hot air inlet 12, circumstance 1 would bepresented.

Circumstance 2.When the control zone 10 is cold and a low staticpressure exists in the hot air inlet 12.

Referring once again to the apparatus shown in FIG- URE l, in thiscircumstance the thermostat 28 develops an increasing temperatureregulated pressure in the thermostat conduit 39 causing thepneumatically operated valve 23 to open to a full position. Because ofthe inadequate static pressure in the hot air inlet 12, less than thepredetermined total volume of air is discharged from the hot air inlet12 into the inlet blending chamber 16. Accordingly the differentialpressure regulator 31 reduces the flow regulated pressure in thepressure regulator conduit 35 causing the pneumatically operated valve22 to move in an open position. As a result, a blend of air from thecold air inlet 11 and the hot air inlet 12 is introduced into the inletblending chamber 16 and thence through the mixing chamber 17 to thedistribution chamber 18 and into the control zone 1% despite the factthat the control zone 10 already is at a temperature below thepredetermined value.

This condition is illustrated graphically in FIGURE 7 where the arrow Eindicates the maximum flow of hot air attainable with a fully openedvalve 23. Because the value indicated by the arrow B is less than thepredeterined value indicated by the arrow A, a quantity of cold airindicated by the shaded area 61 will enter the control Zone 10.

According to a further embodiment of the present invention asillustrated in FIGURE 8, the difiiculties described as circumstance 2can be obviated. The elements of the mixer box shown in FIGURE 8 areessentially the same as those shown in FIGURE 1. merals are employed toindicate corresponding elements.

. The principal change is the provision of a shuttle valve 62 having twoinlet ports 63, 64, one outlet port 65, and one control port 66. Asource of supply air is introduced into a conduit 67 to the inlet port63. The pressure regulator conduit 35a joins the differential pressureregulator 31 with the inlet port 64. A valve operating conduit 68 joinsthe outlet port 65 with the pneumatically operated valve 22. A shuttlevalve operating conduit 69 connects the thermostat conduit 30 with theshuttle valve operating inlet port 66.

The shuttle valve 62 is more fully illustrated in FIG- URE 9.

The valve 62 comprises a hollow casing 70 having an internal chamber 71and the previously mentioned inlet ports 63, 64 and outlet port 65. Anannular boss 72 is provided externally of the casing 70 surrounding aplunger port 73 which extends through the casing 70. A resilientdiaphragm 74 is secured across the outer surface of the annular boss 72by peripheral sealing of a cover plate 75. The diaphragm 74 comprisesthe common wall of two chambers 76 and 77 which are respectively ashuttle valve operating chamber 76 and a vent chamber 77. The shuttlevalve operating port 66 appears in the cover plate 75. Secured to thediaphragm 74 is a flat metal plate 78 and, mounted normally thereto, anoperating plunger 79 which extends through the plunger port 73. A bleedport 88, opening to the atmosphere, extends through the annular boss 72from the vent chamber 77.

Within the shuttle valve chamber 71 and pivotally mounted about a pin 81is a flapper 82 suitably formed from a fiat piece of metal and having atits extreme end a pair of pads 83, 84 of rubber or similar resilientmaterial. A normally compressed spring 85 is positioned with relation tothe flapper 82 to exert a force tending to cause counterclockwisemovement of the flapper 32 whereby the pad 83 covers the tip 86 of thepressure regulator conduit 35a and the pad 84 is displaced from the tip87 of the supply air conduit 67. Opposing the counterclockwise forcepresented by the normally compressed spring 85 is the plunger 79 whichbears against the flapper 82 exerting a clockwise force about the pivotpin 81. The force exerted by the plunger 79 is determined by thepressure maintained within the operating chamber 76, i.e., the pressurewithin the thermostat conduit 69.

Normally the pressure in the operating chamber 76 is sufficient to causethe plunger 7 to overcome the resiliency of the normally compressedspring 85 whereby, under normal conditions, the pad 84 is compressedagainst the tip 87 of the supply air conduit 67 so that a direct flowpassageway is provided from the pressure regulator con duit 35a throughits tip 86 and into the pneumatic controlled valve operating conduit 68.When the temperature regulated pressure in the thermostat conduit 69falls below a predetermined value, the resilient spring 85 causescounterclockwise movement of the flapper 82 whereby the supply airconduit 67 is free to introduce its pressure directly into the conduit68. The pressure of the air in the supply conduit 67 is at all times inexcess of that appearing in the pressure regulator conduit 35a. Undernormal conditions the supply air conduit pressure will be from about 17to 20 pounds per square inch. The pressure in the how regulated pressureregulator conduit 35a will have a range of about pounds per square inch,for example from about 3 to about 8 pounds per square inch. Since thenormal range of pressures in the thermostat conduits 3t), 69 is fromabout 8 to 13 pounds per square inch, the resilient spring 85 producescounterclockwise movement of the flapper 82 only when the pressure inthe operating chamber 76 falls below about 8 pounds per Correspondingnusquare inch. The spring tension of the spring is adjusted to the lowerpressure of the operating range of the pressures in the thermostatconduit 30.

Returning to FIGURE 8, it will be observed that the system operatessatisfactorily under circumstance 2. That is, under normal conditions,the system shown in FIG- URE 8 performs exactly as the system shown inFIG- URE '1.

Where, however, the low pressure maintained in the thermostat conduit 30results in a fully opened valve 23, that same low pressure will activatethe shuttle valve 62 whereby the supply air from the conduit 67 will beintroduced into the conduit 68 to operate the pneumatically controlledvalve 22. By virtue of its normal pressure of 17 to 20 pounds per squareinch, the pressure from the supply air conduit 67 will cause thepneumatically controlled valve 22 to close completely.

Accordingly the characteristics of the system illustrated in FIGURE 8can be graphically represented as shown in FIGURE 10. When thetemperature regulated pressure from the thermostat decreases to a valuebelow its normal operating range, the pneumatically controlled valve 23becomes fully opened and, with a constant static pressure existing inthe hot air inlet 12, the resulting air flow through the hot air inlet12 will be constant as shown by the arrow F. Because of the postulatedlow static pressure in the hot air inlet 12, the flow of air therefromat fully opened position is less than the predetermined flow of air asindicated by the arrow A. Nevertheless, because the thermostaticpressure is below its normal range, the further inflow of cold air isprevented and exclusively hot air is introduced into the inlet blendingchamber 16. Admittedly the total flow of air from the system shown inFIGURE 8 does not, in this one isolated circumstance, have a constantvalue.

A typical situation giving rise to the circumstance 2 occurs in theearly morning in buildings which have been mantained at lower thannormal temperatures throughout the preceding evening during which thebuilding was relatively unoccupied. In the early morning, every room orcontrol zone 10 presents a temperature below the predetermined value andaccordingly every room or control zone requires substantial quantitiesof hot air until the predetermined temperature is attained. Because ofthe universal demand upon the hot air supply, certain periods of lowduct pressure may occur in the hot air inlets 12 through the inabilityof the hot air supply system to provide the peak load requirements. Thusthe system illustrated in FIGURE 8 compensates for a problem whichoccurs daily in the operation of dual duct air conditioning systems.

Having now described its elements the preferred embodiment of thepresent invention may now be quickly illustrated by reference to FIGURE11. The apparatus shown in FIGURE 11 embodies that previously shown inFIGURES 4 and 8., Corresponding numerals are employed to indicatecorresponding elements.

As shown in FIGURE 11, both the shuttle valve 40 and the shuttle valve62 are included in the preferred embodiment. The system shown in FIGURE11 operates exactly, with respect to the shuttle valve 40, as the systemillustrated in FIGURE 4. The system, with respect to the shuttle valve62, operates exactly as that shown in FIG- URE 8. The conduit 30a joinsthe thermostat 28 with the shuttle valve 46. In the preferredembodiment, the shuttle valve operating conduit 69 joins the thermostatconduit 30a with the operating port 66 of the shuttle valve 62.Similarly the pressure regulator conduit conduit 35a joins thedifierential pressure regulator 31 with the inlet port 64 of the shuttlevalve 62. In the preferred embodiment the pressure regulator conduit 41joins the pressure regulator conduit 35a with the inlet port of theshuttle valve 40.

According to the provisions of the patent statutes, I have explained theprinciple, preferred embodiment and mode of operation of my inventionand have illustrated and described what I now consider to represent itsbest embodiment. However, I desire to have it understood that, withinthe scope of the appended claims, the invention may be practicedotherwise than as specifically illustrated and described.

I claim:

1. In an air conditioning mixing and distributing box having a hot airinlet, a cold air inlet and at least one outlet conduit for discharginga blended stream of conditioned air into a relatively confined zone, afluid pressure operated valve in each of said inlet conduits, a sourceof supply air under pressure, flow responsive means adapted to controlthe pressure of a first supply air source as aflow regulated pressure inaccordance with the flow rate of said blended air stream, temperatureresponsive means within said relatively confined zone adapted to controlthe pressure of a second supply air source as a temperature regulatedpressure in accordance with the temperature existing within saidrelatively confined zone, shuttle valve means having two fluid inletsand one fluid outlet adapted to communicate the said fluid outlet withthat fluid inlet having the greater static pressure, conduit meanscommunicating the said temperature regulated pressure and the said flowregulated pressure respectively to the said two fluid inlets and forconnecting the said fluid outlet to the said fluid pressure operatedvalve in the said hot air inlet, and conduit means communicating saidflow regulated pressure to said fluid operated valve in said cold airinlet.

2. In an air conditioning mixing and distributing box having a hot airinlet, a cold air inlet and at least one outlet conduit for discharginga blended stream of conditioned air into a relatively confined zone, afluid pressure operated valve in each of said inlet conduits, a sourceof supply air under premure, flow responsive means adapted to controlthe pressure of a first supply air source as a flow regulates pressurein accordance with the flow rate of said blended air stream, temperatureresponsive means within said relatively confined zone adapted to controlthe pressure of a second supply air source as a temperature regulatedpressure in accordance with the temperature existing within saidrelatively confined zone, conduit means communicating the saidtemperature regulated pressure to the said fluid pressure operated valvein the said hot air inlet, shuttle valve means having two inlet portsand one outlet port, means within said shuttle valve means responsive tothe pressure of said temperature regulated pressure to communicate saidoutlet port with only one of said inlet ports, conduit means connectinga third supply air source to one of said inlet ports and communicatingsaid flow regulated pressure to the other of said fluid inlet ports andfor connecting said outlet port to said fluid operated valve in saidcold air inlet.

3. In an air conditioning mixing and distributing box having a hot airinlet, a cold air inlet and at least one outlet conduit for discharginga blended stream of conditioned air into a relatively confined zone, afluid pressure operated valve in each of said inlet conduits, a sourceof supply air under pressure, flow responsive means adapted to controlthe pressure of a first supply air source as a flow regulated pressurein accordance with the flow rate of said blended air stream, temperatureresponsive means Within said relatively confined zone adapted to controlthe pressure of a second supply air source as a temperature regulatedpressure in accordance with the temperature ex isting within saidrelatively confined zone, first shuttle valve means having two fluidinlets and one fluid outlet adapted to communicate the said fluid outletwith that fluid inlet having the greater static pressure, conduit meanscommunicating the said temperature regulated pressure and the said flowregulated pressure respectively to the said two fluid inlets and forconnecting the said fiuid outlet to the said fluid pressure operatedvalve in the said hot air inlet, second shuttle valve means having twoinlet ports and one outlet port, means within said second shuttle valvemeans responsive to the pressure of said temperature regulated pressureto communicate said outlet port with only one of said inlet ports,conduit means connecting a third supply air source to one of said inletports and communicating said flow regulated pressure to the other ofsaid fluid inlet ports and for connecting said outlet port to said fluidoperated valve in said cold air inlet.

References Cited in the file of this patent UNITED STATES PATENTS2,793,812 McDonald May 28, 1957 2,815,915 Salerno Dec. 10, 19572,821,343 Payne Ian. 28, 1958 Disclaimer 3,026,04L-Arthur P. J entoft,Wexford, Pa. CONDITIONED AIR DISTRIBUTION. Patent dated Mar. 20, 1962.Disclaimer filed Sept. 13, 1962, by the assignee, H. H. RobertsonCompany. Hereb enters this disclaimer to claim 1 of said patent.

Gazette October 25, 1962.]

